It is quite common to apply chemicals on a farm field for one or more purposes. The chemicals can comprise fertilizers, herbicides, fungicides or insecticides for a particular crop predator, for example. In the industry, most manufacturers recommend the application of the chemical uniformly in a quantity of pints per acre of farmland.
In the past, farmers have been forced to premix the chemical with a larger volume of water for spraying onto the farm field by a spray boom attached to a tractor. The farmer was required to calculate the flow rate of the combined chemical water mixture to approximate the density of chemical applied to the farm field. This was inconvenient. It was also inaccurate, as the tractor's speed varied.
Numerous attempts have been made to simplify the farmer's task and deliver the chemicals on a more uniform, accurate basis. U.S. Pat. No. 3,877,645, issued to Oligschlaeger on Apr. 15, 1975 discloses an example of a single tank delivery system with a single mixing tank but delivery rate controlled by vehicle speed. In devices of the type disclosed in this patent, the farmer was still required to mix the chemical and water manually.
Systems such as the device disclosed in U.S. Pat. No. 2,757,044, issued to Gerbracht on July 31, 1956, disclose use of separate chemical and water storage tanks. In the device disclosed in this patent, the water is pumped to a mixing chamber. The chemical is also pumped to the mixing chamber through separate lines by a pump operated from a cam tied directly to a drive wheel on the tractor. The chemical delivery to the mixing chamber is therefore compensated for vehicle speed.
Despite the improvements made in farm chemical delivery, a need still exists for a delivery system having greater versatility. Recent legislation requires systems to be developed which essentially eliminate farmer contact with the chemical. In certain situations, variable density of chemical deposition is desirable and simultaneous deposition of multiple chemicals at varied flow rates can also be desirable. In addition to farming, similar problems exist in the application of road chemicals along a roadway as well as other environments.